You really can't easily take a picture of, or draw, a DLP rainbow. It's more or less a motion artifact.
Think of a image that's made up of three of the same picture, but one is in green, one is in red, and one is in blue. Stacked together the colors blend together to form the finished image. Now think of moving the image rapidly in a direction, but instead of all three layers moving at the same time they move at different speeds, so the individual three colors seperate out and sort of quickly "trail" behind the image. That's one way of describing a rainbow. It's like a colored "flicker" at the corners of your vision, if you see them at all. In any event, that pixelation you see isn't it, you would know a rainbow if you saw it.
I rarely see a rainbow, and even then it's when viewing certain types of material...high contrast white on black test paterns, for instance. It certainly doesn't really bother me...by way of comparision, on my LCD I noticed the "screen door effect" to a greater extent, and that didn't bother me either. FWIW, nobody that's been over has seen RBE either.
Lunchblaze and his wife DO see them, however, so it's definitely a potential side effect. It could have been a too bright image, or they could just be sensitive to that sort of thing.
In any event, they saw then right away, so my point to all of this, Bud, is seriously...don't worry about trying to see them. You don't see them now, so you probally aren't going to see them ever. Could be your screen, your lighting, or just you. But me or anybody giving you tips on how to find RBE would do nothing but point out a weakness that you don't have now.